Many ocean-going vessels now have telephones systems that may call to and be called from any point in the world. One such telephone system is the International Maritime Satellite ("Inmarsat") systems. The Inmarsat organization is a partnership of numerous countries which manages global communications to and from ships, as well as to and from land-based vehicles and aircraft. Because wireless communication is generally line-of-sight and, thus, limited by the earth's curvature, Inmarsat uses satellites to provide wireless connection between any two points on the earth. As will be explained further, below, each of the satellites covers a predefined area of the globe called "ocean regions." An Inmarsat customer may then be reached from anywhere in the world, provided the calling party knows the region in which the Inmarsat customer is located.
In order to call an Inmarsat maritime subscriber, a person dials (from virtually any phone in the world), an access code (AC), the service code (SC), then a 6-9-digit ship identification number. The world is divided into four ocean regions, each of which is designated by an access code, 87X, wherein X equals 1 through 4; in many ways these access codes resemble country codes used for international calls. The regions are: Atlantic Ocean Region-East (871), Atlantic Ocean Region-West (874), Pacific Ocean Region (872), and Indian Ocean Region (873). Currently, the caller has to dial the correct access code of the region where the called ship is located, otherwise the call cannot be completed.
One proposal to insure that all calls can be completed to ships at sea requires a database for keeping track of the location of each ship. Such a database could be a collection of interconnected databases, one local to each switch in the Inmarsat system, or it may be one common database which serves all switches worldwide. The location of each ship would be contained in the database, which location would be updated periodically. The database may be updated by each ship reporting when it crosses a boundary from one region to another, or, alternatively, the database may page each ship and each ship would report its respective location. However, such centralized or interconnected databases are known to be relatively unreliable, because a fault in one small subsystem can cause all information requests to be blocked. Furthermore, such databases would have to have upwards of 500,000 detailed entries, and would, thus, be very memory-consuming and time-intensive in maintenance.
Therefore, a problem in the art is that there is no system for completing calls to a ship at sea as it moves from ocean region to another ocean region.